Functional Description

L9347

14/29

Figure 3.

Input PWM to output current range

The ON period of the input signal is measured with a 1MHz clock, synchronized with the

external 250kHz clock. For requested precision of the output current the ratio between the

frequencies of the input signal and the external 250kHz clock has to be fixed according to

the graph shown in Figure 3.

Figure 4.

Current accuracy according to the input and clock frequency ratio

The theoretical error is zero for fCLK / fIN = 125.

If the period of the input signal is longer than 132 times the period of the clock the regulator

is switched off. For a clock frequency lower than 100kHz the clock control will also disable

the regulator. For high precision applications the clock frequency and the input frequency

have to be correlated.

10

90

250

2250

INPUT PWM[%]

400

800

±10%

+- 6%

+-10%

-10%

5.6%

112.5

132

125

fCLK / fIN

0%

Regulator

switched off